So this is interesting. I used boosting in more places, and for that reason I got across the level quicker. I was ahead by about 20 frames of my other attempt when approaching the boss. However, I'm at the right side of the screen and the screen takes a while to catch back up and it ends up being about 15 frames slower in the end..
Frame 4245 on the revised version, when the boss text appears.
And frame 4230 on the old version, when the boss text appears also.
So that's something to consider as well, and makes things more annoying. Unless you can find a way to make the screen catch up quicker.
Edit Okay, so far I found that sliding backwards for about 2 or so frames and then resuming will put the camera back close to where it should be. I was able to get the boss text at 4218 now, not quite the 20 frames I was ahead by, but still 12.
frame 4218
Added the finished file, Now using the 1.0 version of the Rom. I think it should be correct.
http://tasvideos.org/userfiles/info/18235736872675195
Edit2: So you can apparently manipulate when the boss first appears. I managed to get him to appear quicker. However I messed around on the old test I did, and for some reason he appeared a couple of frames after the boss text appeared. I couldn't get it that fast this time around, but I think with some good RAM watches and rng breakdown, it should be possible. That being said I'm not very good at that.
Here's a comparison (older version first, new version second) of when his tentacle first appears:
Frame 4266.......................................................Frame 4245
Unfortunately I wasn't able to scroll the screen to the right as much as last time, which I believe cuts down on a few lag frames during the fight. Also, that version I got before on a random file, he appeared when the boss meter was around the end of the S in his name. I wanna say that's about ... 10 frames faster, but I'm not sure, I saved over that file since then.